Abstract : Mato Grosso's soybean production has considerably increased in the last ten years reaching 17.9 millions of tons in 2009 (7.2 in 1998). This expansion has led to severe environmental and socio-economical consequences such as deforestation and urbanization. The objective of this study is to assess the efficiency of remote sensing techniques such as NDVI for analyzing the extent of soybean fields in Mato Grosso and the transformation of agriculture in this State. The NDVI was computed from the SPOT-Vegetation sensor on monthly time series (maximum value composition at a 1 km spatial resolution). It enabled locating cultivated areas and monitoring crop growth. It also allowed the detection of the double cropping management practices, which increased drastically in this area for a few years. The results showed a correlation of 0.98 between our estimation of crop areas and IBGE official agricultural statistics for the whole of Mato Grosso. The NDVI time series also confirmed the increase of double cropping systems representing 30% of the cultivated areas in 1999, 57% in 2006 and 67% in 2009. This evolution is an indicator of the agricultural diversification and intensification processes occurring in this region. Moreover, the monitoring of recent large clearings at a local scale (county of Vera) showed a gap reduction between the three successive stages leading to intensified agricultural practices, i.e. forest clearing, first crop plantation and first adoption of double cropping practices. Based on our methodology, we finally proposed a classification of municipalities according to their dominant modes of land use.